1. Field of the Invention
The present invention relates to an organic light-emitting diode (OLED) display and a manufacturing method thereof.
2. Discussion of the Background
The recent trend toward lightweight and thin personal computers and television sets requires lightweight and thin display devices. Hence, flat panel displays are replacing conventional cathode ray tubes (CRT). Flat panel displays include a liquid crystal display (LCD), a field emission display (FED), an organic light-emitting diode (OLED) display, and a plasma display panel (PDP). Among flat panel displays, the OLED display is the most promising because of its low power consumption, fast response time, wide viewing angle, and high contrast ratio. An OLED display is a self-emissive display device that includes an organic light-emitting layer interposed between two electrodes. One electrode injects holes and the other injects electrons into the light-emitting layer. The injected electrons and holes combine to form exitons, which emit light as they discharge energy. An OLED display may be a passive matrix display or an active matrix display according to its driving method. The passive matrix OLED display includes a plurality of anode lines, a plurality of cathode lines crossing the anode lines, and a plurality of pixels, each including a light emission layer. Selecting one anode line and one cathode line causes light emission of the pixel located at the intersection of the selected signal lines. The active matrix OLED display includes a plurality of pixels, and each pixel may include a switching transistor, a driving transistor, and a storage capacitor, as well as an anode, a cathode, and a light emission layer. The driving transistor receives a data voltage from the switching transistor and drives a current having a magnitude corresponding to the data voltage. The current from the driving transistor enters the light emission layer to cause light to emit at an intensity that depends on the current.
Here, input terminals of the driving transistors are commonly connected to driving voltage lines, which supply a driving voltage to the respective driving transistors. Hence, the magnitude of the current flowing through each driving transistor may be defined by the driving voltage as well as the data voltage. In other words, the magnitude of the current may be defined by a difference between the driving voltage and the data voltage.
However, with a larger OLED display, the driving voltages applied to the respective driving transistors may not be uniform. Therefore, when data voltages of equal magnitude are applied to the driving transistors, the driving transistors may not output equal driving currents due to voltage drop, etc. Consequently, the same data voltage may result in different gray scales for displaying images.
Accordingly, a difference between driving voltages due to voltage drop may cause cross-talk, which deteriorates image quality.